Design and characterization of CMOS millimeter-wave transformers

A comprehensive analysis of the impact of geometric parameters on the design of millimeter-wave integrated transformers is presented. Transformers presenting the same stacked topology but different diameters and trace widths were fabricated in a 65 nm CMOS technology and their performance was compared in terms of inductance, quality-factors, coupling coefficient and minimum insertion loss. Results of electromagnetic simulation and measurement are exposed, showing an excellent agreement in a wide frequency band. It is observed that transformers with different diameters present similar performances but different resonance frequencies, whereas transformers with wider traces can present better minimum insertion loss results.